rity; that is, to have particular attracting points or furfaces, whofe attraction is counterbalanced by a certain quantity of latent heat, and which rush together when that heat is fufficiently diminished. Whatever tends to bring the particles into a state more advantageous to their junction, as by presenting their attracting furfaces more directly to one another, forcing them nearer together, removing contrary attractions, &c. muft haften the congelation thus a piece of ice, having its attracting furfaces already in the moft favourable pofition, and their power probably ftronger from their union, promotes the attraction of the particles of the ftill fluid water. He purfues thefe fpeculations at fome length, and concludes them with another rather more unexpected in an experimental enquiry. It feems most probable (he fays) that the particles of matter in general are nothing more than centres to certain attractive and repul five powers; on which hypothefis it may be understood, that if two or more of thefe central points are brought much within the limits of their respective attractions and repulfions, thefe powers will no longer be equal at equai diftances from their common centre. Now fuch a combination of central points may be confidered as one particle of any particular matter; and the unequal diftances from the common centre at which the attractions and repulfions are equal, will define what may be called the shape of that particle. And if, at equal distances, the attraction or repulfion is much greater at one point than at another, that will conftitute a polarity.' Nitrous. Freezing Point. An Account of Experiments made by Mr. John McNab, at Albany Fort, Hudfon's Bay, relative to the freezing of Nitrous and Vitriolic Acids. By Henry Cavendish, Efq. F.R. S. & A. S. In the former paper on this subject *, fome particulars were deduced from reasoning, in a manner which did not ftrike the generality of Strength. readers. with much conviction. The prefent experiments were made to afcertain the truth of it; and their refults agree, for the most part, fufficiently well with the former, except in a few inftances where fome deception had probably happened with refpect to the strengths of the acids. The freezing points, correfponding to the different ftrengths, are now determined, from the whole, as in the annexed table; where the mark means below o, and above o, on Fahrenheit's fcale. The ftrengths are expreffed by the weight of marble which 1000 parts of the acid are capable of diffolving or faturating. This is a very good way of trying, as well as expreffing, the ftrength of nitrous acid; but in See Monthly Review, vol. lxxvi. p. 192. Y 3 568 -45 538 -30 508 18 478 448 4 418 2 4 388 358 328. -18 298 -28 Vitriolic. 977 918 758 -26 +42 -45 trying trying the vitriolic by this method, an uncertainty would arife, on account of the felenite formed in the operation, which somewhat defends the marble from the further action of the acid. The ftrength of this acid was therefore computed from the weight of plumbum vitriolatum, formed by the addition of fugar of lead a quantity of oil of vitriol, fufficient to produce 100 parts of that compound, was found adequate to the faturation of 33 parts of marble; that is, to faturate as much fixed alcali as a quantity of nitrous acid does that would diffolve 33 of marble. Specific gravity would perhaps have been a better criterion, and would likewife have enabled us to compare thefe experiments with Mr. Keir's*; which cannot now be done without very troublesome and delicate experimental investigations, except in one inftance, where Mr. Cavendish has himself determined the gravity of his acid. He informs us, that the gravity of 1,780, the ftrength at which Mr. Keir found oil of vitriol to freeze moft eafily, anfwers to his ftrength of 848, which is very near to the laft but one in the above table: the freezing points allo correfpond very nearly, Mr. Keir's being +46, and Mr. Cavendish's +42. Experiments and Obfervations relating to the Principle of Acidity, the Compofition of Water, and Phlogifton. By Jofeph Priestley, LL.D. F.R.S. That water is compofed of two kinds of air, vital and inflammable, is almoft univerfally admitted as one of the most important, and beft afcertained discoveries of modern chemiftry. "How is it poffible (fays M. Lavoifier, with his affociates †) to doubt of it, when we fee that by burning together 15 grains of inflammable air and 85 of vital air, we obtain exactly 100 grains of water; and that, by the decompofition of water, we recover the fame principles, in the fame proportions? If we could doubt of a truth established on experiments fo fimple, fo palpable, we thould no longer have any thing certain in phyfics; we ought equally to question whether vitriolated tartar be really compofed of vitriolic acid and fixt alcali, fal ammoniac of marine acid and volatile alcali, &c. &c. for the proofs which we have of the com pofition of thefe falts are of the very fame kind, and not at all more rigorous than those which eftablish the compofition of water." When Meffrs. Baumé, Cadet, Darcet, and Sage ‡, *See M. Rev. for March laft, p. 184. + Lavoifier, Bertholet, and Fourcroy, in their report, to the Academy, of Haffenfratz and Adet's new fyftem of chemical characters, June 27, 1787. In their report of the New Chemical Nomenclature, June 23, 1787. See Rev. for July laft, p. 74. ftated ftated to the French Academy their doubts refpe&ting this doctrine, obferving that an immenfe quantity of heat and light is difengaged in the combuftion, and that the water might have been held in folution by this heat, as it is in the atmosphere; the above correspondence in weight was urged as a decifive proof against them, for when 100 grains of the two airs produce exactly 100 grains of water, it is impoffible that all this water could have previously existed in the airs. It appears, however, after all, from the paper now before us, that this correfpondence of weight, on which fo much stress has been laid, and which makes the bafis of the whole doctrine of the compofition and decompofition of water, has actually no existence. Nor, perhaps, is it fo furprifing that inaccuracies and deceptions should happen in experiments of fo much delicacy, as that a theory fo important fhould be raifed, with fo much confidence, on a foundation fo apparently deceitful, and fo infufficiently explored. By repeating, in a more accurate manner, the experiment of the combuftion of the two airs, with due precautions to previously separate from them as much as poffible all extraneous moifture, Dr. Priestley has now found, that the weight of the water produced falls always far fhort of the weight of air decompofed; and, inftead of air being a component part of water, he has made it probable that water is a component part of air. It is already known that inflammable air cannot be produced without water; and the Doctor fhews, by feveral experiments, that the cafe is the fame with respect to fixed air: the aerated terra ponderofa, which appears to have no water in its compofition, yields no fixed air till water is introduced; and 43 or 44 grains of the water are always expended in the production of 100 grains of air; fo that, of this air, water makes near one half. It is probable, that the fame thing obtains in every other kind of air, fince water is employed in the production of them all; that pure water is their proper bafis, or the fubftance without which no aeriform fluid can fubfift; and therefore that water has never been either compofed or décompofed in any of our operations. The water, produced by the combuftion of the two airs, was always found to contain an acid. The experiment was often repeated, and on a large fcale, in order to procure fufficient quan tities of the water for the neceflary trials; and a rigorous examination of it, by Mr. Keir and Dr. Withering, fhewed clearly that the acid is the nitrous. This alfo is an important difcovery; for phlogisticated air has hitherto been thought neceffary to the formation of nitrous acid. Doctor Priestley obierves, that the doctrine of the decompofition of water being fet afide, that of phlogiston (which, in confequence of Y 4 the the late experiments on water, has been almost universally abandoned) will much better ftand its ground, as all the newly dif covered facts are more eafily explained by the help of it; and indeed we do not fee how they can be explained at all without it. He confiders, for inftance, the inflammable air obtained from fulphur and metals by paffing fteam of water over them in a red heat. If this air does not proceed from a decomposition of the fteam, it must receive its principle of inflammability from the fulphur or metal, which therefore cannot be fimple bodies, as the antiphlogistic theory makes them to be. This inflammable fubftance cannot be fuppofed to be real fulphur, or real metal, becaufe, whatever body it be obtained from, it is found always to poffefs the fame properties, to be transferable to other bodies by the fame laws of affinity, and to produce with them the fame compounds. In our preceding account of this volume (See our laft month's Review, page 249) we noticed the meteorological journals, on which the following remark has occurred to us, fince the article was printed, viz. That two observations in the day feem too few for collecting the mean heat of the twenty-four hours; especially when they are made at ftated hours, which hours (7 A. M. and 2 P. M.) are in fome feafons of the year nearly the coldeft and hotteft in the twenty-four, but in other feafons, neither the one nor the other. From our own obfervations, which have been extenfive, and often repeated, at fhort intervals, during the night as well as the day, the greatest cold (excepting in extraordinary circumftances) appears to be, in all feafons, about fun-rife, and the greatest heat about the middle of the interval between noon and fun-fet: but we do not pretend that a medium between these two would be the true mean heat of the 24 hours. To afcertain that, the continuance of the refpective degrees of heat ought to be taken into the account. ART. IX. A short and plain Expofition of the Old Tefiament, with devotional and practical Reflections, for the Use of Families. By the Rev. Job Orton, S. T. P. Published from the Author's MSS. by Robert Gentleman. Vol. I. * Svo. 6s. Boards. Longman, &c. 1783. MR. R. Job Orton was a Diffenting Minifter, of confiderable reputation, at Shrewsbury. Several of his publications ⚫have been commended in our Review. It appears from the pre This work is now printing by fubfcription. The propofals inform us, that it is hoped the whole will be comprifed in five volumes 8vo. but will not exceed fix; that a head of the Author will be engraved; and that an account of his life will be given with the laft volume.' face face to this work, that for more than twenty years he made the expounding of the Scriptures a conftant part of his public fervices. As he apprehended that a fhort and plain expofition of the Old Teftament, with practical reflections at the end of the chapters, was much wanted for the use of families, he (toward the clofe of his life) put the papers, which he had formerly written for the pulpit, into the hands of the Rev. Mr. Palmer of Hackney; earnestly requefting him to prepare them for the prefs. In an advertisement prefixed to this volume, Mr. Palmer fays, Having fuch other engagements as rendered it impoffible for me to proceed in this great work with fuch dispatch as to finish it in any reasonable time, I at length determined to refign it, with all my materials, into the hands of my worthy friend Mr. Gentleman *, who, on various accounts, appeared to me the fitteft perfon I knew to execute the defign of the worthy projector.' Mr. Gentleman, in the preface which follows, gives an account of the manner in which he has proceeded in executing what he conceived to have been the Author's defign. He candidly confeffes, that had the work received the finishing hand of the Author, or been published under his own inspection, it would no doubt have been more complete.' This we can eafily believe; but we think that the generality of plain Chriftians, who have not so much relifh for learned criticifms as for devotional and practical reflections, may find it an agreeable and useful family-book, and as fuch we recommend it. * A Diffenting Minifter at Kidderminster, Worcestershire. ART. X. Military Antiquities refpecting a Hiftory of the English Army, from the Conqueft to the prefent Time. By Francis Grofe, Efq. F. A. S. 4to. 4to. z Vols. 41. 4s. Boards. Hooper. 1788. WE E announced to the Public, in our Review for Sept. 1786, p. 203. that Captain Grofe had publifhed five Numbers of the Military Antiquities; and we then laid before our Readers the proposed objects which the Author had in view. The work is now completed, and its contents will appear from the following account. Although the hiftory commences with the Norman invafion, yet, in order to elucidate his fubject, the Author previously gives a brief description of the military establishment of the AngloSaxons, previous to the time of that event. Perfonal attendance in war, for the defence of the country, being a branch of the Saxon's trinoda neceffitas, obliged every freeman, capable of bearing arms, and not incapacitated by bodily infirmity, in cafe of a foreign invafion, internal infurrection, |